CN102894977B - Interested target body stereo positioning method for electrical impedance mapping imaging - Google Patents

Abstract

The invention discloses an interested target body stereo positioning method for electrical impedance mapping imaging. The interested target body stereo positioning method comprises the following steps of: firstly, performing computational analysis based on an electromagnetic field computational model, and establishing an interested target body depth approximate solution formula; secondly, determining the two-dimensional space position of an interested target body during actual measurement of electrical impedance mapping imaging according to gray level images; and finally, solving to obtain stereo positioning information of the interested target body by establishing and utilizing a method for computing parameters in an electrical impedance mapping detection imaging measured data equivalent representation depth solving formula on the basis. The interested target body stereo positioning method is characterized in that the depth of the interested target body can be measured and calculated by deeply mining detection information on the basis of analysis of features of the two-dimensional gray level images, and stereo positioning of the interested target body is realized.

Description

A kind of interesting target body solid locating method that is mapped to picture for electrical impedance

Technical field

The present invention relates to a kind of electrical impedance imaging objective body solid locating method, particularly relate to a kind of electrical impedance and be mapped to the interesting target body solid locating method in picture.

Background technology

Electrical impedance is mapped to picture and detects the two dimensional gray map image that is generally used for obtaining tested region, the detecting electrode adopting is flat plate array formula electrode (comprising multiple microelectrodes unit), detecting electrode array extracts the body surface current signal in tested region, obtains by the current difference of analyzing between each unit the two dimensional gray map image that reflects objective body electrical impedance distribution under tested region.If there is abnormal impedance disturbance region (being referred to as interesting target body) in electrod-array under certain several detecting electrodes unit, these detecting electrode unit are compared other electrode electrode units around and can be obtained larger current signal, are reflected in two-dimensional map gray-scale map and present " bright group " feature.The plane relative position of interesting target body can be reflected in " bright group " in two-dimensional map gray-scale map, but can not reflect depth information, therefore cannot position interesting target body relatively accurately.Electrical impedance is mapped in the research of picture both at home and abroad at present, only limits to utilize two dimensional gray map image to differentiate the plane relative position of interesting target body, because detection information is not yet fully excavated, cannot carry out solid location to interesting target body.

Summary of the invention

Current electrical impedance is mapped to while looking like to carry out image discriminating, cannot directly directly estimate the interesting target body degree of depth from the two dimensional gray map image of imaging gained, therefore also cannot carry out solid location to interesting target body in tested region relatively accurately, for this defect or deficiency, the object of the invention is to, propose a kind of electrical impedance and be mapped to the solid locating method of picture to interesting target body, the method is on the basis of analysis of two-dimensional gray scale map image feature, detect information by deep excavation, can calculate the degree of depth of interesting target body, improve the accurately precision of location of interesting target body.

In order to realize above-mentioned task, the present invention adopts following technical solution:

The three-dimensional location of an interesting target body estimating and measuring method that is mapped to picture for electrical impedance, is characterized in that, comprises the following steps:

1), based on the computational analysis of Electromagnetic Calculation model, set up interesting target body degree of depth approximate solution formula;

2) be mapped in picture actual measurement in electrical impedance, determine the two-dimensional space position of interesting target according to gray level image;

3) set up electrical impedance and be mapped to the corresponding relation as actual measurement numerical value and interesting target body degree of depth approximate solution Parameters in Formula;

4) the space two-dimensional information of interesting target body is combined with the depth information of objective body, obtains the space multistory positional parameter of interesting target body.

Described calculates and sets up interesting target body degree of depth approximate solution formula based on Electromagnetic Calculation model, and solution procedure is:

1), in the time that electromagnetic field model calculates, the electric field perturbations area-of-interest that setting interesting target body causes is mainly distributed in the domed region under detecting electrode face, supposes that disturbance interesting target body is approximately spheroid simultaneously.

2) in the time that electromagnetic field model calculates, in surveyed area, comprise respectively interesting target body and do not comprise under these two kinds of conditions of interesting target body, solve the expression on detecting electrode surface;

3) utilize the current information of detecting electrode plane and the positional information of respective electrode unit to represent the degree of depth in interesting target region, obtain the depth solving formula of interesting target body.

Key parameter in described interesting target body degree of depth approximate solution formula comprises i (x ₀, y ₀), i ⁰(x ₀, y ₀), i (a, b), i ⁰(a, b), wherein i (x ₀, y ₀) be that its electrode coordinate of measured value of interesting target body center, projected area on detecting electrode face is (x ₀, y ₀), i ⁰(x ₀, y ₀) be interesting target body while not existing corresponding to electrode coordinate (x ₀, y ₀) measured value located, i (a, b) the interesting target body measured value that outside center, projected area, arbitrary coordinate (a, b) is located on detecting electrode face, i ⁰(a, b) is the measured value that interesting target body is located corresponding to electrode coordinate (a, b) while not existing.

The described electrical impedance of setting up is mapped to the corresponding relation as actual measurement numerical value and interesting target body degree of depth approximate solution Parameters in Formula, the steps include:

1) be first mapped to as two dimensional gray figure and determine the view field scope of interesting target body in detecting electrode plane according to electrical impedance;

2) solve the meansigma methods I of all measured values of interesting target body beyond in detecting electrode plane projection region _mean;

3) determine the corresponding greatest measurement I of interesting target body _max, and the corresponding electrode unit coordinate of this greatest measurement (X _max, Y _max);

4) determine half peak I of interesting target body measured data curve in detecting electrode plane projection region _half, i.e. I _half=1/2 (I _max-I _mean), and further find and approach I _halfthe measured data of value the coordinate (X of corresponding detecting electrode unit _half, Y _half);

5) set up the corresponding relation of each parameter in actual measurement numerical value and degree of depth approximate solution formula.

The described corresponding relation of setting up each parameter in actual measurement numerical value and degree of depth approximate solution formula is, while bringing actual measurement numerical value the calculating of into degree of depth approximate solution formula, to use I _maxsubstitute i (x ₀, y ₀), use I _halfsubstitute i (a, b), use I _meansubstitute i ⁰(x ₀, y ₀) and i ⁰(a, b).

The present invention has fully excavated electrical impedance and has been mapped to the detection information of picture, the electrical impedance realizing is mapped to the interesting target body solid locating method in picture, can be in obtaining interesting target body two dimensional gray imaging results, utilize the degree of depth of detecting electrode measured data estimation interesting target apart from detecting electrode face, for being mapped to picture, electrical impedance detects the method that a kind of accurate location interesting target body interested is provided, and significant in actual applications.

Brief description of the drawings

Fig. 1 is that electrical impedance mapping detects equivalent schematic.

Fig. 2 is that electrical impedance mapping detects interesting target depth solving model schematic diagram.

Fig. 3 is that electrical impedance is mapped to picture two dimensional gray mapping graph key message point coordinates schematic diagram.

Fig. 4 is the corresponding relation figure that electrical impedance is mapped to picture two dimensional gray mapping graph and one-dimensional measurement curve.

Fig. 5 is the three-dimensional distribution map that electrical impedance is mapped to picture measurement data.

Fig. 6 is that electrical impedance is mapped to picture physical model.

Fig. 7 is that electrical impedance is mapped to as carrying out interesting target test experience figure in physical model.

Fig. 8 is the imaging results of objective body at physical model.

Fig. 9 is the comparison diagram that adopts degree of depth estimation result and actual grade.

The present invention is described in further detail for the embodiment providing below in conjunction with accompanying drawing and inventor.

Detailed description of the invention

For further illustrating feature of the present invention and advantages characteristic, the present embodiment provides the solid estimation scheme of abnormal impedance interesting target body (pathological changes enclosed mass) when a kind of tissue resistance is anti-is mapped to picture detection.

Fig. 1 is that bio-electrical impedance mapping detects equivalent schematic, the electrical impedance characteristics that normal structure is compared pathological tissues has significant difference, can be similar to and think that the interior normal structure of surveyed area is uniformly distributed, if there is pathological changes enclosed mass, can cause local electrical impedance disturbance, be referred to as interesting target body, and suppose that interesting target is approximate spheroid.Be below concrete solution procedure:

Step 1: be mapped to the testing conditions of picture according to electrical impedance, set up Maxwell equation group the electromagnetic field on surveyed area inside and surface thereof is described, and be similar to according to the equivalence of model, the constraints of equation group is set.

If surveyed area three dimensions is Ω, measurement electrode plane is Г, and exciting electrode surface is γ, the conductivity that σ+i ω ε is tissue, and any point r=(x, y, z) that is positioned at three dimensions Ω meets following absorbing boundary equation group:

$\left\{\begin{array}{cc}\▿\·((\mathrm{\σ}+\mathrm{i\ω\ϵ})\▿\left(r\right))=0,& r\∈\mathrm{\Ω}\\ V\left(r\right)=0,& r\∈\mathrm{\Γ}\\ V\left(r\right)=1,& r\∈\mathrm{\γ}\\ (\mathrm{\σ}+\mathrm{i\ω\ϵ})\▿\left(r\right)\·v\left(r\right)=0,& r\∈\∂\mathrm{\Ω}\backslash (\mathrm{\Λ}\∪\mathrm{\γ})\end{array}\right.$ (formula 1)

Because the responsive detection zone of the current perturbation of detecting electrode plane Г to the generation of interesting target body mainly concentrates in the region of detection plane Г below, further we are in domed region as shown in Figure 1 and Figure 2 by the region of interest definition of analysis of electric field.If the length of side of detecting electrode plane Г is 2L, the radius of domed region is L.As shown in Figure 2, the constraints of solving equations arranges as follows:

${\mathrm{\&Gamma;}}_L:=\{(x,y,0):\sqrt{x^2+y^2}<L\},$

${\mathrm{\&Omega;}}_L:=\{(x,y,z):z<0,\sqrt{x^2+y^2+z^2}<L\}$

Conductivity is defined as

Normal structure: τ ₁=σ ₁+ i ω ε ₁r ∈ Ω _ld

Pathological tissues: τ ₂=σ ₂+ i ω ε ₂r ∈ D

Step 2: comprise interesting target body and do not comprise under these two kinds of conditions of interesting target body in surveyed area, asking respectively the expression at detecting electrode place under two kinds of conditions according to Maxwell equation group.

(1) when interesting target body exists, the electric current density at detecting electrode plate place solves

On the surface of lesion region D, electromotive force V meets

and there is V ^int=V ^ext, wherein V ^intand V ^extbe defined as respectively the electromotive force of the inside and outside both sides of D region surface.The voltage everywhere in Fig. 2 establishes an equation under meeting:

$\left\{\begin{array}{cc}\mathrm{\&Delta;}{V}^{\mathrm{ext}}\left(r\right)=0& r\&Element;{\mathrm{\&Omega;}}_L\backslash \stackrel{\&OverBar;}{D}\\ \mathrm{\&Delta;}{V}^{\mathrm{int}}\left(r\right)=0& r\&Element;D\\ V^{\mathrm{int}}\left(r\right)=V^{\mathrm{ext}}\left(r\right)& r\&Element;\&PartialD;d\\ {\mathrm{\&tau;}}_{1}v\left(r\right)\&CenterDot;\&dtri;V^{\mathrm{ext}}\left(r\right)={\mathrm{\&tau;}}_{2}v\left(r\right)\&CenterDot;\&dtri;V^{\mathrm{int}}\left(r\right)& r\&Element;\&PartialD;D\\ V\left(r\right)=0& r\&Element;{\mathrm{\&Gamma;}}_L\\ {\mathrm{\&tau;}}_1\frac{\&PartialD;}{\&PartialD;z}V\left(r\right)=-i\left(r\right)& r\&Element;{\mathrm{\&Gamma;}}_L\end{array}\right.$ (formula 2)

I (r) is the electric current density that flows out measurement electrode plate.

(2) during without pathological changes enclosed mass, the electric current density at (interesting target does not exist) detecting electrode plate place solves in hypothesis surveyed area does not have pathological tissues, and relevant voltage electric current (having 0 subscript) meets:

$\left\{\begin{array}{cc}\mathrm{\&Delta;}{V}^0\left(r\right)=0& r\&Element;{\mathrm{\&Omega;}}_L\\ V^0\left(r\right)=0& r\&Element;{\mathrm{\&Gamma;}}_L\\ {\mathrm{\&tau;}}_1\frac{\&PartialD;}{\&PartialD;z}{V}^0\left(r\right)=-i^0\left(r\right)& r\&Element;{\mathrm{\&Gamma;}}_L\end{array}\right.$ (formula 3)

Wherein i ⁰(r) there is no in the situation of pathological tissues the electric current density at detecting electrode face place in surveyed area.

Step 3: bring green theorem into Maxwell equation group, equation group is dissolved, finally utilize the current information of detecting electrode plane and the positional information of respective electrode unit to represent the degree of depth in interesting target region.

This step is mainly utilized detection plane Γ _lon information representation lesion region D:

By green theorem substitution formula 2.If Φ (r, r') is the solution of the green theorem in infinite space.Wherein

ΔΦ (r, r')=δ (r-r'), r ∈ Γ _l, r' ∈ Ω _l.

According to green theorem, above-mentioned equation group has been done to a series of derivations, the final purpose of derivation is to use Γ _lelectric current in plane represents the various information of area-of-interest D.After above-mentioned Formula Series abbreviation, obtain:

$\begin{array}{c}({\mathrm{\&tau;}}_1-{\mathrm{\&tau;}}_2)\frac{\&PartialD;}{\&PartialD;z}{\&Integral;}_D\frac{{\&dtri;}_{r^{\&prime;}}V\left(r^{\&prime;}\right)\&CenterDot;(r^{\&prime;}-r)}{4\mathrm{\&pi;}{|r-r^{\&prime;}|}^3}{\mathrm{dr}}^{\&prime;}\&ap;\\ \frac{1}{2}[i\left(r\right)-i^0\left(r\right)],r\&Element;{\mathrm{\&Gamma;}}_{L/2}\end{array}$ (formula 4)

Spheroid or while approaching spheroid, above formula further abbreviation is at D:

$\frac{1}{2}[i\left(r\right)-i^0\left(r\right)]\&ap;\frac{3{\stackrel{\&OverBar;}{i}}^0({\mathrm{\&tau;}}_1-{\mathrm{\&tau;}}_2)}{2{\mathrm{\&tau;}}_1+{\mathrm{\&tau;}}_2}\left|D\right|\frac{-{(x-x_0)}^2-{(y-y_0)}^2+{{2\mathrm{<figure-callout\; id="0"\; label="z"\; filenames="1.png"\; state="\{\{state\}\}">z</figure-callout>}}_0}^2}{4\mathrm{\&pi;}{|r-{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="1.png"\; state="\{\{state\}\}">r</figure-callout>}}_0|}^5}$ (formula 5)

Wherein, r ∈ Γ _l/2, | D| represents the volume of D.From this formula, just can derive the degree of depth at area-of-interest position.

Definition (x ₀, y ₀) be the center of D projected area on Γ, establish (a, b) for any point outside upper heart position, D projected area on Γ, establish d for (a, b) is to (x ₀, y ₀) distance,

the depth z of D ₀can draw by following formula:

$\frac{|i(a,b)-i^0(a,b)|}{|i(x_0,y_0)-i^0(x_0,y_0)|}=\frac{|2-\frac{d^2}{{{\mathrm{<figure-callout\; id="0"\; label="z"\; filenames="1.png"\; state="\{\{state\}\}">z</figure-callout>}}_0}^2}|}{2{(\frac{d^2}{{{\mathrm{<figure-callout\; id="0"\; label="z"\; filenames="1.png"\; state="\{\{state\}\}">z</figure-callout>}}_0}^2}+1)}^{5/2}}$ (formula 6)

For the ease of understanding, in the present embodiment, (a, b) is defined as to reference electrode point.

Step 4: utilize electrical impedance mapping to be detected as the method for calculating parameter in picture measured data equivalence sign depth solving formula, wherein electrical impedance mapping is detected as measured data and refers to and the corresponding measured value of two dimensional gray imaging results; Equivalence characterizing method refers to by the immeasurability parameter in measurable parameter approximate representation depth solving formula.

According to formula 6, need to utilize electrical impedance mapping to be detected as the parameter characterizing as measured data has i (x ₀, y ₀), i ⁰(x ₀, y ₀), i (a, b), i ⁰(a, b).Concrete characterizing method is as follows:

(1) i (x ₀, y ₀), be the measured value of D center of projected area on Γ, (x ₀, y ₀) be corresponding coordinate figure.As shown in Fig. 3, Fig. 4, Fig. 5, in actual measurement data, i (x ₀, y ₀) the maximum I in " speck " region in corresponding two dimensional gray figure _mean, its coordinate figure of electrode unit corresponding to this maximum place is (X _max, Y _max).

(2) i ⁰(x ₀, y ₀), while existence for D, coordinate (x in Γ plane ₀, y ₀) measured value located.In actual measurement, this value cannot directly measure, and the approximation can only exist with D time in detecting electrode face gained measured value substitutes.While existence due to D, corresponding result when measured result is equivalent to be all even normal structure in surveyed area, as shown in Figure 4 in two dimensional gray imaging the corresponding normal structure of black region testing result, so the meansigma methods I of the corresponding measurement data of available black region _meanreplace i ⁰(x ₀, y ₀).Fig. 5 is the distributed in three dimensions of D detecting electrode gained measured value while existing, can select the corresponding measured value I of each electrode unit of flat site _meanmeansigma methods replace.

(3) i (a, b), is D measured value of any point in projection center outer projection region on Γ, and (a, b) is corresponding coordinate figure.In actual applications, according to half peak I of selection of the present invention " speck " region corresponding detecting electrode plane measured data curve _half(I _half=1/2 (I _max-I _mean)) equivalence sign i (a, b), as shown in Figure 4.

(4) i ⁰(a, b), while existence for D, the measured value that in Γ plane, coordinate (a, b) is located.The same i of equivalently represented method of this measured value ⁰(x ₀, y ₀), can think and i ⁰(x ₀, y ₀) value equate.

Further, according to formula 6, use I _maxsubstitute i (x ₀, y ₀), use I _halfsubstitute i (a, b), use I _meansubstitute i ⁰(x ₀, y ₀) and i ⁰(a, b), can obtain the degree of depth estimated value of interesting target body, further combined with the plane coordinates information in two dimensional gray figure, can carry out space orientation to interesting target body.

According to interesting target body solution formula 6, and parameter equivalent characterizing method in step 4, we further adopt physical model to carry out the actual estimation to interesting target, and method is as follows:

Adopt as the physical model of Fig. 6, the equally distributed normal structure of saline solution analog electrical impedance in model as shown in Figure 7, is used the abnormal interesting target body of agar block analog electrical impedance characteristic.By changing the distance of agar block apart from detecting electrode array, can obtain different measurement results.The size of agar block is got 5mm × 5mm × 5mm, 8mm × 8mm × 8mm, and tri-kinds of specifications of 12mm × 12mm × 12mm, detect the degree of depth and are respectively 5mm, 10mm, 15mm.Its electrical impedance mapping imaging results in physical model as shown in Figure 8.Further we adopt the method for formula 6 and step 4 to estimate the degree of depth of interesting target body, and contrast with the actual grade of interesting target body, and result as shown in Figure 9.This experiment can further illustrate the present invention and can be electrical impedance and be mapped to picture the method for a kind of accurate location interesting target body of providing is provided.

It should be noted that, above embodiment is convenient to understand the present invention, and the present invention is not limited to this embodiment, and correction, interpolation and replacement that those skilled in the art carry out according to technical solution of the present invention all should belong to the scope of protection of the invention.

Claims (3)

1. the three-dimensional location of an interesting target body estimating and measuring method that is mapped to picture for electrical impedance, is characterized in that, comprises the following steps:

1), based on the computational analysis of Electromagnetic Calculation model, set up interesting target body degree of depth approximate solution formula;

2) be mapped in picture actual measurement in electrical impedance, determine the two-dimensional space position of interesting target body according to gray level image;

3) set up electrical impedance and be mapped to the corresponding relation as actual measurement numerical value and interesting target body degree of depth approximate solution Parameters in Formula;

4) the space two-dimensional information of interesting target body is combined with the depth information of objective body, obtains the space multistory positional parameter of interesting target body;

Described interesting target body degree of depth approximate solution formula is as follows:

$\frac{|i(a,b)-i^0(a,b)|}{|i(x_0,y_0)-i^0(x_0,y_0)|}=\frac{|2-\frac{d^2}{{z_0}^2}|}{2{(\frac{d^2}{{z_0}^2}+1)}^{5/2}}$ Formula (6)

Wherein i (x ₀, y ₀) be that its electrode coordinate of measured value of interesting target body center, projected area on detecting electrode face is (x ₀, y ₀), i ⁰(x ₀, y ₀) be interesting target body while not existing corresponding to electrode coordinate (x ₀, y ₀) measured value located, i (a, b) the interesting target body measured value that outside center, projected area, arbitrary coordinate (a, b) is located on detecting electrode face, i ⁰(a, b) is the measured value that interesting target body is located corresponding to electrode coordinate (a, b) while not existing;

D is that (a, b) is to (x ₀, y ₀) distance, $d=\sqrt{{(x_0-a)}^2+{(y_0-b)}^2};$

Z ₀represent the interesting target body degree of depth;

Further, according to formula (6), use I _maxsubstitute i (x ₀, y ₀), use I _halfsubstitute i (a, b), use I _meansubstitute i ⁰(x ₀, y ₀) and i ⁰(a, b), can obtain the degree of depth estimated value of interesting target body, further combined with the plane coordinates information in two dimensional gray figure, can carry out space orientation to interesting target body;

Wherein, I _meanfor the meansigma methods of all measured values of interesting target body beyond in detecting electrode plane projection region, I _maxfor the corresponding greatest measurement of interesting target body, I _halffor half peak value of interesting target body measured data curve in detecting electrode plane projection region.

2. the method for claim 1, is characterized in that, described sets up interesting target body degree of depth approximate solution formula based on Electromagnetic Calculation model, and solution procedure is:

1), in the time that electromagnetic field model calculates, the electric field perturbations area-of-interest that setting interesting target body causes is mainly distributed in the domed region under detecting electrode face, supposes that disturbance interesting target body is approximately spheroid simultaneously;

2) in the time that electromagnetic field model calculates, in surveyed area, comprise respectively interesting target body and do not comprise under these two kinds of conditions of interesting target body, solve the expression on detecting electrode surface;

3) utilize the current information of detecting electrode plane and the positional information of respective electrode unit to represent the degree of depth in interesting target region, obtain the depth solving formula of interesting target body.

3. the method for claim 1, is characterized in that, the described electrical impedance of setting up is mapped to the corresponding relation as actual measurement numerical value and interesting target body degree of depth approximate solution Parameters in Formula, and its step is as follows:

1) be first mapped to as two dimensional gray figure and determine the view field scope of interesting target body in detecting electrode plane according to electrical impedance;

2) solve the meansigma methods I of all measured values of interesting target body beyond in detecting electrode plane projection region _mean;

3) determine the corresponding greatest measurement I of interesting target body _max, and the corresponding electrode unit coordinate of this greatest measurement (X _max, Y _max);

4) determine half peak I of interesting target body measured data curve in detecting electrode plane projection region _half, i.e. I _half=1/2 (I _max-I _mean), and further find and approach I _halfthe measured data of value the coordinate (X of corresponding detecting electrode unit _half, Y _half);

5) set up the corresponding relation of each parameter in actual measurement numerical value and degree of depth approximate solution formula.

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